Battery-driven appliances, such as vacuum cleaners, lawn mowers and hand tools, are becoming increasingly popular. Vacuum cleaners like GD 911 or Backuum from the applicant, lawn mowers like Rotak 34 LI from Bosch, or hand-held power tools are examples of such appliances.
An appliance like that has three major parts: a battery pack, a charger for the battery, and the appliance it self. Such appliances usually have three different electronic systems, which are used for controlling the discharge and re-charge of the appliance. The first electronic system is part of the battery and controls or monitors the temperature and voltage of the cells inside the battery. The second electronic system is normally part of the charger and controls the charging voltage and current supplied to the battery during re-charging. The third electronic system is part of the appliance and comprises an on/off switch and control means for controlling features like revolution speed, soft start of the motor, automatic switching between battery packs, protection against deep discharge of the battery pack, or other control features.
In some stick-type vacuum cleaners the first and second electronic systems are omitted, so that the charger is coupled directly to the battery in the cleaner without having any intelligence controlling the charging of the battery. These models have the disadvantage that the charging (and discharging) of the battery cannot be adjusted according to the performance of the battery.
EP 2014423 A2 discloses a charger for charging various types of battery packs, which uses a wireless or electrical connection to communicate with the individual battery packs. The charger comprises an identification module, which is capable of receiving the identification information or detecting the identification means from the battery pack. The battery packs are charged or discharged according to their characteristics, which are transmitted to and from the battery to the charger or the power tool.
US 2004/0121223 A1 and WO 2009/128082 A1 both disclose a battery pack having a plurality of battery cells connected to a plurality of switches controlled by a controller inside the battery. The controller uses the switches to selectively charge or discharge the battery cells according to the measured voltage of each cell or the required load configuration. The battery pack is connected to an external charger or load device, which transmits commands to the controller inside the battery.
US 2004/0217737 A1 relates to cordless power systems and more particularly to a controller system in which the cordless system components include a cordless power device, a battery pack and a charger. The electronic system (204), which controls the charging of the battery pack, is placed outside the battery pack itself just as the electronic system (10) for controlling the external device is placed outside the pack itself, i.e. in the external device. Thus, the battery pack does not contain an electronic system for controlling the charging, neither does it contain an electronic system for controlling the external device.
Instead the battery packs is connected to an external discharge/charge circuitry, which transmits a discharge or charge signal to a switch controller inside the batteries. The switch controller selectively couples the battery pack to the discharge or charge path, while preventing cross-conduction between the battery packs.
US 2006/0087286 A1 discloses a cordless power system. The system includes a cordless power tool a battery pack and a charger. The battery pack is mated with either the cordless tool or the battery charger. Both the battery pack and the battery charger are equipped with an intelligent circuit, i.e. a battery electronic control and a charger electronic control, respectively. Also the power tool is equipped with a tool electronic control. Thus the system comprises at least three different electronic systems each mounted in the three components, i.e. tool, battery pack and charger.
In these configurations, the electronic systems are located in the charger, battery pack and appliance or in the battery pack and the appliance, respectively. This increases the number of components used to control the charging and discharging of the battery pack, which increases the production costs of the major parts. Furthermore, if the charger or the appliance is to be able to handle multiple battery packs at the same time, this requires a number of redundant circuits or systems for charging and discharging the battery packs, which increases the complexity of the systems and the production costs.